Background and objectives

The successful application of bioremediation technology for degradation of environmental pollutants may require that genetically modified micro-organisms be introduced into the environment. Because of their perceived novelty, it is necessary to evaluate such GMOs for any potential risks associated with their release into the environment. It is also necessary to assess their survival and ability to degrade pollutants.


Approach and methodology

Two pollutant-degrading, genetically modified micro-organisms were studied. Both carried genetic modifications affecting the catabolic pathways for degradation of substituted aromatic compounds. The strains were introduced into contained activated sludge and soil microcosms, and their behaviour was evaluated. Three factors were assessed: first, the effects of physico-chemical and biological variables on the survival and activity of the strains; second their ability to degrade pollutants in situ; and third the frequency of transfer of recombinant DNA from the strains to other micro-organisms. The third of these phenomena was evaluated as a risk associated with the introduction of the GMO into the environment.

Main findings and outcome

The strains survived in activated sludge and in sterile soil. However, survival depended on the physico-chemical and biological conditions. The modified strains degraded pollutant compounds added to the microcosms via the modified degradation pathways. The genetic material introduced into the chromosome of these GMOs did not transfer to other micro-organisms. However, recombinant DNA on plasmids could be transferred to other micro-organisms and expressed. Transfer maintenance and expression of the DNA was dependent on the type of recipient micro-organism. The rate of transfer was also dependent on the nutrient level in the environment, the temperature, and the degree of agitation. This work demonstrates that genetically modified micro-organisms can be used for bioremediation.

Conclusions

This work was the first to demonstrate that genetically modified organisms, in this case micro-organisms, specifically designed to degrade pollutant compounds did indeed express the desired activities, and thereby degrade the target pollutants in conditions found in the environment. The project thus confirms that GMOs may have a contribution to make in cleaning up environmental pollution. However, to ensure containment of the introduced genes, any recombinant DNA should be integrated into chromosome of the modified strains, and not carried on plasmids.